Desalting crude oils



ZAESS l May 2S 394@ B. L.. Evi-:RING ET AL y DSALTING CRUDE OLSl Filed July 14, 1945 xSQQ GEM um.

@N Gm QOLYQYQMM NGQUR@ Nbxx France ay as, rare DESALTEIG CRUDE @ILS Application July 14,1945, Serial No. 605,018

Claims.

This invention relates to improvements in the removal of inorganic salts from crude oil. Inorganic salts in the form of chlorides of'sodium, magnesium and/or calcium arefrequently associated with crude petroleum oils, usually in the form of a salt brine emulsiied with the oil; or in the form of crystalline salts usually surrounded by an oil film. The removal of salt from such crude oils by the usual methods present diiiicult problems. For example, when contacting the salt-containing oil with water, the oil iilm around the salt particles prevents the Water from coming in contact with the salt crystal and as a consequence methods employing the washing of crude oil with hot water are not eective; even the addition of a demulsifying agent to the water has relatively small eiect. The present invention provides a method for` reducing the salt content of crude oil to a relatively low gure.

The removal of salt from crude oils prior to any distillation process or cracking process is necessary, since the presence of these salts, particu. larly when the concentration of salt exceeds about pounds per 1000 barrels of oil, gives rise to considerable diiculties. They form deposits upon the heating surfaces and in the heating tubes o i the heating equipment, such as stills, heat exchangers and the like, reducing its heating transfer' capacity, they plug equipment and give rise to serious corrosion problems.

It is an object of the present invention to provide an improved method of desalting crude petroleum oils. Another object of the invention is to provide a method of removing inorganic salts, such as the chlorides of sodium, magnesium Land/or calcium from crude petroleum oils withmethod of carrying out the herein-described i11.

vention.

In accordance with the present invention, saltcontaining crude petroleum oils or salt-contant ing reduced crude oils, particularly such oils containing more than about 20 pounds of salt per i000' barrels of oil are eiective desaltedto at least a salt content below that which is considered detrimental, by treating such oils with liquid anhyorous hydrogen fluoride. The presence of large amounts of inorganic chlorides such as sodium,

calcium and magnesium chlorides in crude oils is highly undesirable, since as Ahereinbeiore earth chlorides to the water insoluble iiuorides,

which however are soluble in the liquid hydrogen iiuoride. `These fluorides beingless readily A,hy-

drolyzed do not form corrosive products; furthermore any remaining inorganic salts settle out.

more readily due to the emulsion destabilizing effect of the hydrogen fluoride treatment.

Generally, depending upon the amount of salt in the crude and the operating conditions from about 0.006 volume percent to about 60 volume percent or more of anhydrous -I-IF can suitably be employed under pressures sumcient to maintain the hydrogen fluoride and the oil in the liquid phase. The amount of vanhydrous hydrogen fluoride used can. vary over a wide range, of from a trace sulcient only to react with the inorganic chlorides present in the crude oil, to as much as about 60 volume percent of HF when it is desired to operate with a liquid anhydrous HF layer.

` Depending upon the reaction temperatures and the quantity of hydrogen uoride employed, pres- Y sure of from about atmospheric pressure to about 150 pounds per `square inch can be used. A contact time of from about one minute to about one hundred and twenty minutes or more is suitable, although a contact time of from about ve minutes to about sixty minutes is usually suficient.y

The treatment is suitably conducted at temperatures of from about 25 F. to about 150 F., although temperatures of from about 32 F. to about 100 F., for example, temperatures of 70 to F. are preferred. While it is preferred to carry out thedesalting process at these tempera` tures, temperatures as high as about 400 F. can be used. At these higher temperatures pressures as high as about 1500 pounds per square inch are employed. y

ln carrying out the present invention, the salt# containing crude oil can be treated with stoichiometrical amounts of hydrogen iluoride'to convert the chlorides to the corresponding fiuorides,

drogen fluoride.

tion removed from the system. The amount of hydrogen fluoride to be employed can be predetermined by an analysis of the salt content of the crude o'il prior to the treatment with the hy- Since the hydrogen chloride, which is largely responsible for the corrosion 'in the processing of salt-containing crude oil, is removed from the system, and since the inorganic fluorides which are formed are more resistant to decomposition to form corrosive products, the hydrogen fluoride treated crude oil can be processed z without encountering difficulties encountered by processing crude oils containing inorganic chlorides.

However, in a preferred embodiment of the,

- introduced via line I I into the reactor I2, wherein it is contacted with liquid anhydrous hydrogen fluoride from storage tank I3, introduced via pump I4 and line I5. The crude oil from source Il is preferably first freed of the maior portion of any water which may bepresent in the crude oil as it is received from the lwells by well-known demulsifying and water removal means. Also, if the crude oil is highly viscous, it is desirable to lower the viscosity'thereof by diluting the same bon diluent, such as hexane, saturated petroleum vnaphtha, or a liquefied normally gaseous saturated hydrocarbon, such as propane and the like. A hydrocarbon diluent oil from the source Itcan be introduced via :line I1 into line Il, wherein it is admixed with the crude oil to be treated. The reactor I2 is suitably Jacketed to provide means l for controlling the temperature within the reactor, and if desired, can be provided with heating coils (not shown) in the bottom portion thereof.

, with a diluent, preferably a paraflinic hydrocar- The extractor I2 is suitably a packed tower type i reactor to provide thorough and intimate mixing and contacting of the crude oil and the hydrogen fluoride, although other suitable means of obtaining intimate contact can be employed. A temperature of 32 F. to 100 F., preferably of about 70 F. to 80 F, is maintained in the reactor and under a pressure sufficient, for example, from f about atmospheric pressure to about 150 pounds --per square inchto maintain the reactants in the liquid phase. Gaseous hydrogen chloride is with` -drawn from the reactor through a line I8, while 4the mixture of crude `oil and liquid hydrogen fluoride are withdrawn from the reactor. I2 through a line I9` and introduced into a separator 2II, wherein the mixture is permitted to'separate into a lower hydrogen fluoride layer and an upper crude oil layer containing small amounts of liquidl hydrogen fluoride. and possibly small 'amounts of hydrogen chloride. The crude oil layer from the'upper portion of the separatorl 20 is passed via line 2i through a. preheater 22, wherein it is heated to a temperature of from about 200 F. to about 450 F. and then introduced into a stripper 23. In the stripper 23, which is provided with heating means such as a heating A moved via a line I2.y

v and the hydrogen chloride formed in the reacis maintained at a pressure of about 30 to 50 pounds per square inch, the desalted crude oil is heated to a temperature of from about 350 F. to about 500 F., to free it of hydrogen fluoride together with some hydrogen chloride. The hydrogen fluoride and hydrogen chloride are withdrawn from stripper 23 through a line 25 and a condenser -26 to a flash drum 21 wherein hydrogen chloride is flashed off and withdrawn through vent 28, Hydrogen fluoride from drum 21 is withdrawn via line 2l and condenser 30 and introduced into line I5, and either recycled to the reactor I2 or sent to thestorage tank I3.' The desalted crude oil stripped of hydrogen fluoride, is withdrawn from the stripper 23 via line'il, and

it necessary, passed through a fluoride removal' system 32 to remove any fluorides which may have been carried over from the reactor I2. 'I'he fluoride removalsystem is suitably a conventional bauxite tower or other suitable system to insure the substantial removal of any remaining fluorides which may be contained in the desalted crude oil. The desalted crude oil, substantially free of fluorides, is removed from the fluoride re-v F., and preferably between about F, and 450 F., by means of a heating.y coil 38. The hydrogen fluoride from the tower 21 is passed via line 3l through a condenser 40 to a receiver 4I. The

` bottoms from the tower 21 which comprise inorganic fluorides and sludge-like materials is re- Water inevitably enters the system through crude oil feed stock and/or make-up hydrogen fluoride. To prevent this water from building up in the system, it is removed by Icy-passing a portion of the hydrogen fluoride from the tower 31 through lines 38 and land heat exchanger a to a hydrogen fluoride-water azeotrope distillation tower 44, provided with a suitable heating means 45 in the bottom portion thereof. The hydrogen fluoride-waterazeotrope in the tower Il is maintained at avtemperatu're of from about F. to about 240 F. at atmospheric pressure and anhydrous hydrogen fluoride removed overhead through lines 48 and I8 and condenser 40 to the receiver 4I, while aqueous hydrogen fluoride is removed from the bottom of tower M through a line". A portion of the anhydrous hydrogen fluoride in the receiver 4I Iis returned through pump 40 and line I9 to the top of the tower Il to serve as reflux. The hydrogen fluoride Yin the receiver 4I can be passed via line l0 and pump 5I tothe storage tank I3.

'I'he eifectiveness of liquid anhydrous hydrogen fluoride in desalting crude petroleum oils is demonstrated by the following example in which a crude petroleum oil comprising 75% Slaughter Crude Oil and 25% Wasson Crude Oil, and which contained about 216 pounds of salt per 1000 barrels of crude oil, was used. This crude oil composition was treated with 200 cubic centimeters ot liquid anhydrous hydrogen fluoride per liter C011 24 in the bottom Portionthereot, and whichi u of crude oil at a temperature ot about 78 F. for

acciones drogen fluoride per liter of crude oil were addedv to the ralnateand the mixture stirred for about thirty minutes at a temperature of about 77 F. The mixture was then permitted to separate into a ramnate layer and an extract layer andthe latter then separated from the former. The rafiinate layer was then heated to a temperature of about 400 F. to remove the last traces of hydrogen uoride. During the treatment of the saltcontaining crude oil with the hydrogen fluoride, the gas formed during the reaction was vented and analyzed as hydrogen chloride as evidenced by the formation of a heavy white precipitate when the gas was passed over a silver nitrate solution. The effective removal of salt is shown by the data in the following table:

Liquid HF (ca/liter of crude oil) Lbs. salt per 1000 bbls. of crude oil Crude oil The above data show that the hydrogen fluoride treatment of the crude oil resulted in the removal 4of 94% of the salt to give a iinal value `of 13.3 pounds of salt per 1000 barrels oi' crude oil. This is a marked improvement over conventional desalting methods which leave about 25 to 40 pounds of salt per 1000 barrels of crude oil.

While the present invention has been described by way of a specic example thereof, it is not intended that the same be limited tothe particular example which has been given merely for the sake of illustration, nor by any theory as to the mechanism of operation of the invention, but only the appended claims in which it is intended to claim all otherv modications coming within the scope and spirit thereof.

We claim: v

l. The method of desalting a crude petroleum oil containing inorganic chlorides selected from the group consisting of alkali metal chlorides and alkaline earth chlorides comprising contacting said crude oil with liquid anhydrous hydrogen fluoride in an amount and for a time sumcient to convert said chlorides to lluorides with the formation of hydrogen chloride and removing said hydrogen chloride.

2.' The method oi' desalting a crude petroleum oil con lnoc chlorides selected. from the group consisting of alkali metal chlorides and alkaline earth chlorides comprising contacting said crude oil with at least stoichiometrical amounts, based on said inorganic chloride content of said crude oil, of liquid anhydrous hydrogen fluoride for a time suiiicient .to convert said chlorides.to luorides with a formation of hydrogen chloride and removing said hydrogen chloride.

3. The method of desalting crude petroleum oil containing inorganic chlorides selected from the group consisting of alkali metal chlorides andalkaline earth chlorides comprising treating said crude oil with liquid anhydrous hydrogen fluoride in sufficient quantities to react with substantially all of the chlorides, whereby said inorganic chlo rides are converted to iluorides with the formation of hydrogen chloride, removing said hydrof gen chloridev from the liquid products, and removing unreacted hydrogen uoride from the treated crude oil.

4. The method of desalting crude petroleum oil containing inorganic chlorides selected from the groupconsisting of alkali metal chlorides and alkaline earth chlorides comprising contacting said crude oil with liquid anhydrous hydrogen fluoride in sucient quantities and under conditions to convert said chlorides to iluorides with the formation of hydrogen chloride and to form a diphasic separation of a ralnate phase comprising said crude oil substantially free of inorganic salts, and an extract'phase, comprising liquid hydrogen uoride containing therein inorganic fiuorides, removing hydrogen chloride from ad the reactor, separating said ramnate and removing vhydrogen iuoride from the said railinate.

5. The method of desalting crude petroleum oil containing inorganic chlorides selected from the group lconsisting of alkali metal chlorides and d0 alkaline earth chlorides comprising contacting .said crude oil with liquid anhydrous hydrogen fluoride in a contacting zone, in sumcient quantities and under conditions to convert said chlorides to iluorides with the formation oi hydrogen chloride and to form a diphasic separation of a ralnate phase comprisingsaid crude oil substantially free of inorganic salts and an extract phase comprising liquid hydrogen fluoride containing therein vinorganic fiuorides, removing hy.- drogen chloride from the reactor, separating said ramnate phase and said extract phase and recovering hydrogen uorlde fromsaid raiilnate l and extract phase, and recycling the recovered hydrogen fluoride to said contact'zone. 

